/*-
 * Copyright (c) 1998 Brian Somers <brian@Awfulhak.org>
 *                    with the aid of code written by
 *                    Junichi SATOH <junichi@astec.co.jp> 1996, 1997.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD: src/sys/netinet/libalias/alias_cuseeme.c,v 1.13.8.1 2009/04/15 03:14:26 kensmith Exp $");

#ifdef _KERNEL
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/module.h>
#else
#include <errno.h>
#include <sys/types.h>
#include <stdio.h>
#endif

#include <netinet/in_systm.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/udp.h>

#ifdef _KERNEL
#include <netinet/libalias/alias.h>
#include <netinet/libalias/alias_local.h>
#include <netinet/libalias/alias_mod.h>
#else
#include "alias_local.h"
#include "alias_mod.h"
#endif

#define CUSEEME_PORT_NUMBER 7648

static void
AliasHandleCUSeeMeOut(struct libalias *la, struct ip *pip,
              struct alias_link *lnk);

static void
AliasHandleCUSeeMeIn(struct libalias *la, struct ip *pip,
             struct in_addr original_addr);

static int
fingerprint(struct libalias *la, struct ip *pip, struct alias_data *ah)
{

    if (ah->dport == NULL || ah->oaddr == NULL)
        return (-1);
    if (ntohs(*ah->dport) == CUSEEME_PORT_NUMBER)
        return (0);
    return (-1);
}

static int
protohandlerin(struct libalias *la, struct ip *pip, struct alias_data *ah)
{

    AliasHandleCUSeeMeIn(la, pip, *ah->oaddr);
    return (0);
}

static int
protohandlerout(struct libalias *la, struct ip *pip, struct alias_data *ah)
{

    AliasHandleCUSeeMeOut(la, pip, ah->lnk);
    return (0);
}

/* Kernel module definition. */
struct proto_handler handlers[] = {
    {
      .pri = 120,
      .dir = OUT,
      .proto = UDP,
      .fingerprint = &fingerprint,
      .protohandler = &protohandlerout
    },
    {
      .pri = 120,
      .dir = IN,
      .proto = UDP,
      .fingerprint = &fingerprint,
      .protohandler = &protohandlerin
    },
    { EOH }
};

static int
mod_handler(module_t mod, int type, void *data)
{
    int error;

    switch (type) {
    case MOD_LOAD:
        error = 0;
        LibAliasAttachHandlers(handlers);
        break;
    case MOD_UNLOAD:
        error = 0;
        LibAliasDetachHandlers(handlers);
        break;
    default:
        error = EINVAL;
    }
    return (error);
}

#ifdef _KERNEL
static
#endif
moduledata_t
alias_mod = {
       "alias_cuseeme", mod_handler, NULL
};

#ifdef  _KERNEL
DECLARE_MODULE(alias_cuseeme, alias_mod, SI_SUB_DRIVERS, SI_ORDER_SECOND);
MODULE_VERSION(alias_cuseeme, 1);
MODULE_DEPEND(alias_cuseeme, libalias, 1, 1, 1);
#endif

/* CU-SeeMe Data Header */
struct cu_header {
    u_int16_t   dest_family;
    u_int16_t   dest_port;
    u_int32_t   dest_addr;
    int16_t     family;
    u_int16_t   port;
    u_int32_t   addr;
    u_int32_t   seq;
    u_int16_t   msg;
    u_int16_t   data_type;
    u_int16_t   packet_len;
};

/* Open Continue Header */
struct oc_header {
    u_int16_t   client_count;   /* Number of client info structs */
    u_int32_t   seq_no;
    char        user_name [20];
    char        reserved  [4];  /* flags, version stuff, etc */
};

/* client info structures */
struct client_info {
    u_int32_t   address;/* Client address */
    char        reserved  [8];  /* Flags, pruning bitfield, packet
                     * counts etc */
};

static void
AliasHandleCUSeeMeOut(struct libalias *la, struct ip *pip, struct alias_link *lnk)
{
    struct udphdr *ud = ip_next(pip);

    if (ntohs(ud->uh_ulen) - sizeof(struct udphdr) >= sizeof(struct cu_header)) {
        struct cu_header *cu;
        struct alias_link *cu_lnk;

        cu = udp_next(ud);
        if (cu->addr)
            cu->addr = (u_int32_t) GetAliasAddress(lnk).s_addr;

        cu_lnk = FindUdpTcpOut(la, pip->ip_src, GetDestAddress(lnk),
            ud->uh_dport, 0, IPPROTO_UDP, 1);

#ifndef NO_FW_PUNCH
        if (cu_lnk)
            PunchFWHole(cu_lnk);
#endif
    }
}

static void
AliasHandleCUSeeMeIn(struct libalias *la, struct ip *pip, struct in_addr original_addr)
{
    struct in_addr alias_addr;
    struct udphdr *ud;
    struct cu_header *cu;
    struct oc_header *oc;
    struct client_info *ci;
    char *end;
    int i;

    (void)la;
    alias_addr.s_addr = pip->ip_dst.s_addr;
    ud = ip_next(pip);
    cu = udp_next(ud);
    oc = (struct oc_header *)(cu + 1);
    ci = (struct client_info *)(oc + 1);
    end = (char *)ud + ntohs(ud->uh_ulen);

    if ((char *)oc <= end) {
        if (cu->dest_addr)
            cu->dest_addr = (u_int32_t) original_addr.s_addr;
        if (ntohs(cu->data_type) == 101)
            /* Find and change our address */
            for (i = 0; (char *)(ci + 1) <= end && i < oc->client_count; i++, ci++)
                if (ci->address == (u_int32_t) alias_addr.s_addr) {
                    ci->address = (u_int32_t) original_addr.s_addr;
                    break;
                }
    }
}
